High-pressure discharge lamps for photo-optical purposes are produced using two sealing techniques—film or rod sealing. Discharge lamps using rod sealing are produced using so-called valve-seat or capillary sealing. One example of valve-seat sealing is DE-A 30 29 824. DE-A 196 18 967 discloses a high-pressure discharge lamp which uses a seal with capillaries as a support for the electrode system.
Until now, the loose support of capillary lamps—the capillary seal—has been formed directly adjacent to the lamp bulb. In addition to the formation of the loose support (capillary seal), the bulb must also be shaped by a shaping tool in the junction area between the bulb and the shaft. Discontinuities and undesirable deformation occur in the bulb wall, influencing the unimpeded emergence of light. The problem is illustrated in FIG. 1. In this case, the high-pressure discharge lamp 1 is equipped with a cathode 2 and an anode 3. The area of the capillary seal 4 has a circle around it. In this case, the ends of the bulging bulb 5 of the discharge vessel are passed over the shaft 6 of the two electrodes, which are connected to the electrical supply lines which project out of the inner part. The pump stalk 7 is seated at half the height directly on the bulb in the shadow of the anode. In the area of the capillary tube, the glass of the bulb is guided very close to the shaft of the electrode, in order to mechanically fix it. The actual sealing area is located behind this.